University Controlling Energy Costs With Direct-Contact Heat Recovery

The Richard J. Renaud Science Complex on the campus of Concordia University in Montreal is a 345,000-sq-ft, L-shaped structure consisting of a salvaged 1960s building, a new eight-story north wing, and a new four-story south wing. The general layout of each wing is similar. Laboratories are located in the central core of the building, with offices on the perimeter. A public corridor separates the laboratories from the offices, while a private technical corridor divides the laboratories into two sections.

When the university embarked on construction of the complex, a central issue was ensuring the safety and quality of the air within the wet laboratories, which contain 250 fume hoods and occupy 45 percent of the building. Other criteria, including strict adherence to green-building principles and the highest standards of heating efficiency, came into play as well.

VENTILATION FOR MULTIFUNCTION BUILDING

The university opted for a variable-air-volume (VAV) ventilation system with terminal reheat for both laboratory and non-laboratory functions of the north wing and another system for the other parts of the complex. The north-wing system consists of four 80,000-cfm modules, while the south-wing system consists of two 80,000-cfm modules. In each building, these modules supply air in two vertical shafts and then distribute it to a horizontal network on each floor.

“The VAV system provides more operational flexibility than a constant-volume system …,” Nicolas Lemire, P.Eng., co-leader of the project-management team of PMA-Pellemon, a joint venture of Montreal-based engineering firm Pageau Morel, said. “Combining labs and offices in our VAV modules supplies more fresh air than is required by recognized standards in all areas. Furthermore, while meeting containment objectives, the VAV system can be adjusted locally to provide the desired amount of air at the right temperature and right relative humidity in each individual room.”

OPTIMIZING ENERGY EFFICIENCY

In the complex, heat is recovered from laboratory exhaust, electrical and telecommunications rooms, and growth chambers and nuclear-resonator rooms and recycled for air-heating purposes. A low-temperature heating loop is used to cool chiller condenser water, basically using centrifugal chillers as heat pumps. The idea was to recover everything from building/campus installations before resorting to other sources of energy.

The complex's two steam boilers are equipped with a custom-engineered heat-recovery system based on Sofame Technologies' Hybrid Percomtherm “direct-contact” condensing stack economizer, which is equipped with an integral fully modulating burner.

“Direct-contact heat-recovery technology was the most logical way of controlling energy costs since it can recuperate nearly 100 percent of the heat in a boiler's flue gas at gas temperatures as low as 50°F,” Luc Mandeville, P.Eng., Sofame's vice president of engineering, said.

Yves Gilbert, P.Eng., director of engineering and building-performance facilities management for Concordia University, added: “Since the Science Complex was built, we estimate that our direct-contact heat-recovery system delivers annual savings of approximately 285,929 cu m of natural-gas-fuelled energy. In terms of dollars and cents, that amounts to annual savings of approximately $157,260.”

ASHRAE TECHNOLOGY AWARD

In 2005, Lemire and PMA-Pellemon project-management-team co-leader Roland Charneux, P.Eng., were presented the top American Society of Heating, Refrigerating and Air-Conditioning Engineers Technology Award in the institutional-building category. The award was clear recognition that air quality and heating efficiency not only can be “green,” but can be achieved within affordable budget parameters, with long-term maintenance-cost savings.